Microwave has no power

F7 means power to magnetron is interrupted.

I don't recommend that someone without experience and an understanding of the safety procedures undertake troubleshooting this.
You can find manuals and helpful exploded view diagrams for your model here and my favorite parts supplier is here. There is a technical sheet hidden behind the controls that has helpful technical and troubleshooting information. It will say something like this:

F7 Power to magnetron interrupted

1. Unplug microwave oven or disconnect power.
2. After 40 seconds, check to see whether this solves the problem.
3. Unplug microwave oven or disconnect power.
4. Check cooling fan operation
5. Check the magnetron.
6. Check P65 connection on the relay control board.
7. Check the P56/P66 connection between relay board and relay control board.
8. Check wiring to the 1200W inverter and control system. See "Checking Inverters."
9. Check operation of all interlock switches.
10. Replace all parts and panels before operating.
11. Plug in microwave oven or reconnect power.
12. Check voltage at 4903-1 on relay board. If it is 120, unplug microwave oven or disconnect power.
13. Replace inverter.
14. Replace all parts and panels before operating.
15. Plug in microwave oven or reconnect power.
16. If problem persists, unplug microwave oven or disconnect power.
17. Replace relay control board.
18. Replace all parts and panels before operating.
19. Plug in microwave oven or reconnect power.
20. If problem persists, unplug microwave oven or disconnect power.
21. Check for reversed plug connection on controls or loose wiring.
22. Replace all parts and panels before operating.
23. Plug in microwave oven or reconnect power.

William E. Miller, AS-EET
http://www.MicrowaveControl.com
Microwave Oven Control Panel Repair Nationwide
"Recycling by repairing since 1982"

The magnetron thermal protector probably shut the oven down. Magnetrons don't like it when their load impedance is too low (empty oven or popcorn) and they get quite warm. Operating an oven empty also shortens the life of the magnetron.

If you need further help, I’m available over the phone at https://www.6ya.com/expert/david_29ad5d1dd86564b0

Hi,
Here is a tip that will help you to figure out what is wrong with yourMicrowave Oven....

Microwave Oven Basic Troubleshooting Tips

heatman101

sounds like a key panel or control board

Assuming yours is a model KHMS2050SSS0, here is what the technical sheet says about the F7 error code:

1. Unplug microwave oven or disconnect power.
2. After 40 seconds, check to see whether this solves the problem.
3. Unplug microwave oven or disconnect power.
4. Check cooling fan operation
5. Check the magnetron.
6. Check P65 connection on the relay control board.
7. Check the P56/P66 connection between relay board and relay control board.
8. Check wiring to the 1200W inverter and control system. See “Checking Inverters.”
9. Check operation of all interlock switches.
10. Replace all parts and panels before operating.
11. Plug in microwave oven or reconnect power.
12. Check voltage at 4903-1 on relay board. If it is 120, unplug microwave oven or disconnect power.
13. Replace inverter.
14. Replace all parts and panels before operating.
15. Plug in microwave oven or reconnect power.
16. If problem persists, unplug microwave oven or disconnect power.
17. Replace relay control board.
18. Replace all parts and panels before operating.
19. Plug in microwave oven or reconnect power.
20. If problem persists, unplug microwave oven or disconnect power.
21. Check for reversed plug connection on controls or loose wiring.
22. Replace all parts and panels before operating.
23. Plug in microwave oven or reconnect power.

(This troubleshooting guide presumes one does not know how to test electronic components. That's why they say to replace and part and check it again.)

You can find helpful exploded view diagrams and order parts by entering your full model number from the tag on the oven here.

If yours is a different model number, please reply back.

check for a blown ceramic fuse behind the panel. If the fuse is dark in color it is probly bad. you can get one at radio shack store or on line

There should also be a "mini-manual" (tech sheet) hidden inside the unit behind the control panel or hidden on the left side behind the grille, which is very helpful when troubleshooting, testing, and locating components.

It says:

F7 Power to magnetron interrupted

1. Unplug microwave oven or disconnect power.
2. After 40 seconds, check to see whether this solves the problem.
3. Unplug microwave oven or disconnect power.
4. Check cooling fan operation
5. Check the magnetron.
6. Check P65 connection on the relay control board.
7. Check the P56/P66 connection between relay board and relay control board.
8. Check wiring to the 1200W inverter and control system. See “Checking Inverters.”
9. Check operation of all interlock switches.
10. Replace all parts and panels before operating.
11. Plug in microwave oven or reconnect power.
12. Check voltage at 4903-1 on relay board. If it is 120, unplug microwave oven or disconnect power.
13. Replace inverter.
14. Replace all parts and panels before operating.
15. Plug in microwave oven or reconnect power.
16. If problem persists, unplug microwave oven or disconnect power.
17. Replace relay control board.
18. Replace all parts and panels before operating.
19. Plug in microwave oven or reconnect power.
20. If problem persists, unplug microwave oven or disconnect power.
21. Check for reversed plug connection on controls or loose wiring.
22. Replace all parts and panels before operating.
23. Plug in microwave oven or reconnect power.

If for some reason your tech sheet is not there, you can download it here.

We regularly repair control units for customers nationwide by mail for $39.95 postpaid in about a week with a one-year guarantee.

Feel free to contact me directly (and please remind me of your full model number) for more information & help.

We're happy to help you with free advice and we'd appreciate your thoughtful rating of our answer.

William E. Miller
[email protected]
http://www.microwavedisplay.com

F7 is q Power to magnetron
interrupted

1. Unplug microwave oven or disconnect power.
2. After 40 seconds, check to see whether this solves the problem.
3. Unplug microwave oven or disconnect power.
4. Check cooling fan operation
5. Check resistance of the magnetron thermostat.
6. Check the magnetron.
7. Check P2, P4 and P27 connections.
8. Check wiring to the 1100W inverters and control system. See
“Checking Inverters.”
9. Check operation of all interlock switches.
10. Replace inverter, if defective.
11. Replace all parts and panels before operating.
12. Plug in microwave oven or reconnect power.
13. If problem persists, unplug microwave oven or disconnect power.
14. Replace electronic control.
15. Replace all parts and panels before operating.
16. Plug in microwave oven or reconnect power.
17. If problem persists, unplug microwave oven or disconnect power.
18. Check for reversed plug connection on controls or loose wiring.
19. Replace all parts and panels before operating.
20. Plug in microwave oven or reconnect power.

If you think the window is stained, you ought to see the rest of the inside! Wife is probably right. (wink, wink, nod, nod)
Actually, you can take the cover off, remove the front panel without much effort and clean everything and get a lot more life out of it. Microwaves usually die because of heat related problems caused by buildup of yuck on the guts.
Hope Ya Make your Wife Happy!